Add widget subarea style

IPython/html/static/notebook/less/widgetarea.less

@@ -0,0 +1,8 b''
+
+/* This class is for the widget subarea inside the widget_area and after
+   the prompt div. */
+div.widget_subarea {
+    padding: 0.44em 0.4em 0.4em 1px;
+    margin-left: 6px;
+    .box-flex1();
+}

IPython/html/static/notebook/less/style.less

@@ -11,5 +11,3 b''
 @import "savewidget.less";
 @import "toolbar.less";
 @import "tooltip.less";
-
-

IPython/html/static/style/style.min.css

@@ -1584,3 +1584,4 b' span#checkpoint_status,span#autosave_status{font-size:small;}'
 .ipython_tooltip .tooltiptext pre{border:0;-webkit-border-radius:0;-moz-border-radius:0;border-radius:0;font-size:100%;background-color:#f7f7f7;}
 .pretooltiparrow{left:0px;margin:0px;top:-16px;width:40px;height:16px;overflow:hidden;position:absolute;}
 .pretooltiparrow:before{background-color:#f7f7f7;border:1px #ababab solid;z-index:11;content:"";position:absolute;left:15px;top:10px;width:25px;height:25px;-webkit-transform:rotate(45deg);-moz-transform:rotate(45deg);-ms-transform:rotate(45deg);-o-transform:rotate(45deg);}
+div.widget_subarea{padding:0.44em 0.4em 0.4em 1px;margin-left:6px;-webkit-box-flex:1;-moz-box-flex:1;box-flex:1;}